LED in London within 5 years

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LED in London within 5 years

Post by Kaustav »

I know one should not believe EVERYTHING that the newspapers publish.... BUT..... today I read in The Independent (Sunday) that there is a trail in Barnet, Southwark and Greenwich with L.E.D. street lighting that is claimed to consume 40% less energy with plans on making the whole of the Londo region LED lit within five years. Now, my questions are:

a) are the new LED lights designed with good shielding so that the light is directed where it's meant to go? (probably not!)
b) what's the chance that they just make the lights look fancy without any consideration for stray light?
c) if the LED lights ARE shielded well I wonder if these type of lights will contribute towards reducing sky glow and general LP?
d) is it easier or more difficult to filter out LED lighting using LP filters (narrow and broadband pass)?

Hmmm.... opinions, anyone?

Kaustav Bhattacharya
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Post by Vega »

I'd imagine the colours that might used on these LEDs could be harder to filter out (while not filtering out wavelengths that we want to see). Imagine if they went for pure white or blue lights :shock:

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Post by Deimos »

I have no idea about them or the trial but, the fact that there is a triial after which there will be a review is probably very useful. The fact of a trial/review gives a fantastic opportunity for people to write in with comments during the trial. Thus, if the lights are not well shielded or are too bright, or whatever, then everybody should write in to comment on these issues – not to stop the idea but so they can modify it and go for something that addresses the comments received.

Thus, anybody living in or passing through the trial area can help a lot by passing on their experience allowing others to write-in. I assume the Campaign for … will be doing this but maybe if they could let people know the nature of the problems and where to write to.

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Post by 12dstring »

LEDs themselves are very directional, so I would assume the new lights would be very directional too. I think most new lights are designed this way anyway (they are around where I live anyway).
The LEDs in the lamp would presumably be pointing downwards (the lamp designers should be shot if otherwise) in which case very little light could escape upwards, if any.
This would leave any upwards glow solely responsible by reflections from the ground, which is much less than any direct upward lighting.

The downside is that the lights would most likely be white, and so could not be filtered out (using narrow or broadband LP filters) unlike the narrow wavelength Sodium lamps.
However, the Sodium lamps shine directly about 30% of their light emission above the horizontal, whereas it would be negligable with LED lamps.

I can't say for certain, but I would think that properly directed broadband light would have less impact than undirected but filtered narrowband light. It'd also be much better for naked eye observing too. As well as the obvious advantage of much better efficiency and not breaking for years and years.
Personally I welcome the change.

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